1. Field of the Invention
The present invention relates to the stiffness measurement of creases in packet blanks.
2. Brief Description of the Prior Art
Pre-formed creases in packet blanks of carton board or similar material must be of acceptable stiffness or problems, expensive in terms of down time costs, are likely to occur in the operation of packaging machines to which the blanks are fed. Thus if a crease is of too great a stiffness value, an adhesive seam involving a panel bounding the crease may spring open. Such failure of the seam could lead to jamming of a packaging machine mechanism.
It is a common practice in the manufacture of blanks for hinged lid cigarette packets to form as many as fifty-six individual blanks from a single sheet of carton board. If it is desired to test for stiffness six creases of each blank, 336 crease tests must be made, and even this large number of tests yields for each of the fifty-six die stations only a single test value fo reach of the creases. Using presently available test apparatus capable of testing only one crease at a time and requiring prior preparations of a test specimen cut from the blank, the attainment of test data is very time consuming. Moreover, presently available crease stiffness test apparatus is not capable of providing adequate running efficiency predictors of modern high-speed packaging machinery.